It is well known that "pitch" can accumulate in various areas of papermaking machinery causing significant problems. The term "pitch" as used herein, refers to the sticky materials which form insoluble deposits in pulp and paper making processes. These sticky materials may originate from the wood from which the paper is made, or as more recycled paper is being used in paper making processes, the term is frequently used as a more general term to include all sticky material which is soluble in organic solvents but not soluble in water, and includes, for example, ink or adhesive material present in recycled paper. The depositing material originating from recycled fiber has also been called "stickies", however, for purposes of this invention, the term "pitch" shall include not only naturally occurring pitch particles derived from paper pulp, but also any synthetic sticky materials derived from recycled fiber and which form insoluble deposits in paper making processes.
Pitch is known to accumulate at various points in the papermaking system. For example, it is known to block the paper machine felts and thus hinder drainage of the paper web. It can adhere to the wires or drying cylinders causing it to pick holes in the paper. It may also deposit on press rolls, dryer fabric or other like equipment which come into direct or indirect contact with the paper sheet or paper machine felts. In fact, all paper machine fabrics and many of the rolls which contact the fabrics or paper sheet will, from time to time, accumulate deposits of pitch.
Many materials and techniques have been used in an attempt to eliminate these problems. Traditional techniques to control these deposits have been to either shut down the production equipment to clean off the affected equipment parts or to treat all of the contaminants in the system with various chemical compositions such as inorganic treatments including talc or anionic dispersants. However, conventional dispersants have been generally ineffective in closed systems due to the accumulation and build-up of pitch. In such closed systems the pitch particles must be removed from the water system in a controlled way without being allowed to accumulate on the paper machine felts or rolls or, for example, the pipe work used in the paper making machinery.
It is known to spray aqueous formulations of certain cationic polymers and/or cationic surfactants onto various paper machine surfaces which are in contact with the process water and which are prone to deposit formations to reduce the build-up of these deposits. However these treatments have been limited to those areas of the papermaking process which is in contact with the process water in order to facilitate removal of the pitch deposits from the system. It has now been found, that those areas of the papermaking machine which are not in contact with the process water, i.e. the dryer fabrics, dryer rolls, and the like, may advantageously be treated with polymeric compositions to effectively control pitch from depositing thereon.